Theatrum Chemicum Britannicum (1652) image via Public Domain Review
"Sacred Geometry" refers to the assigning of sacred connotation to geometric shapes and proportions. The concept is thought to have originated in ancient Greece with the idea that the universe follows a distinct plan or pre-defined pattern. The geometric ideal heavily affected the physical world of religious structures including some of the most well-known; churches, mosques and temples. The concept of holy space extends to sacred groves, Magic Circles, holy altars and modern occult art. Many of the earliest references place "The Creator" or Godhead at the center; a great engineer figure that can be found in such faiths as Hinduism (The Manasara), Christianity and Islam.
The Metatron Cube a symbol using Sacred Geometry that is a metaphor for the known connected universe.
The dome of the Florence Cathedral. The geometry of the dome is taken from the sphere a representing heaven. Image via Wikipedia
Hermetic occultism and other distinct occult schools use symbols such as; The Unicursal Hexagram, the circled dot (the alchemical symbol for the sun), and the pentacle in practice or identification. The pentacle was an ancient marking of a circled five-pointed star, which was only later pointed upside-down for use in Satanism. The symbol was further altered in the Sigil of Baphomet used by The Church of Satan. Aleister Crowley used the Unicursal Hexagram's powerful shape with a five-petalled flower to represent cosmic forces in the Thelema. The unique pointed star shape in the Unicursal Hexagram can be drawn with one single continuous line.
Sigil of Baphomet used by The Church of Satan
Naberius seal or sigil is the pictorial signature of a Demon or other supernatural being
Robert Fludd's illustration of man the microcosm within the universal macrocosm. Fludd (1574 – 1637ad) was a English physician and author with scientific and occult interests.
Robert Fludd, Utriusque Cosmi, 1619 image vi Wikipedia
"Seal of God" Sigillum Dei Aemeth a magical diagram thought to give power over all creatures (Expect Archangels) by John Dee author of Monas Hieroglyphica
Alchemy Sulfur Symbol also known as a 'Leviathan Cross' or 'Satan's Cross' image via wikipedia frequently used to represent Satan The Morning Star.
The Seventy-Two Goetia Sigils from The Book of the Goetia of Solomon the King by S.L. MacGregor Mathers and Aleister Crowley. This file is licensed under the Creative Commons Attribution-Share Alike 4.0 International license.
Occult Symbolism in Dark Art
The general use of Art and symbol in cult and magic rituals has been employed since at least the Neolithic era and was used throughout ancient cultures. These early representations have evolved into a rich Artistic tradition with symbol and markings as diverse as the the sigils of Occultist Austin Osman Spare and symbology of modern avant-garde filmmaker Alejandro Jodorowsky. Beyond providing a visual language for the hidden mysteries of this world, they've also inspired current Artists to incorporate their visual stamp.
Letter-press print of the Tree of Life drawn by modern Artist Damien Echols. Image via the Artists Site